The present invention relates to improved surgical instruments and, more particularly, to an improvement to the craniotome. A craniotome is well known as a surgical instrument utilized in performing a craniotomy where a series of bur holes are first drilled in the skull and then a craniotome is used to cut between bur holes. After several bur holes have been cut and the craniotome utilized to cut between adjacent bur holes, a section of the skull may thus be removed.
It is well known that there are a series of three meninges or membranes which cover the brain, the outermost of which is the dura mater, commonly referred to as the dura. The dura is thus positioned between the brain and the underside of the skull itself. When performing a craniotomy it is desirable to avoid tearing, cutting or rupturing the dura. However, the dura tends to adhere to the underside of the skull and this adherence becomes more pronounced in more elderly subjects. Furthermore the dura is more fibrous with increasing age and thus easier to tear with tool movement.
Prior to the present invention the safest technique for stripping or removing the dura was laborious, tedious, and painstakingly slow. After first drilling bur holes, the procedure includes inserting a long, thin spatula through a bur hole to strip a portion of the dura from the underside of the skull between two bur holes. Then the surgeon removed the spatula, and inserted a craniotome and cut the skull between these two bur holes, then removed the craniotome and re-inserted the spatula to strip the dura from the underside of the skull between the next pair of bur holes. Thereafter, the craniotome was re-inserted, an additional cut was made, the craniotome removed, the spatula re-inserted, and additional dura stripped from the underside of the skull. Thus it may be appreciated that only a short segment of the dura could be stripped at a time and thereafter a corresponding short segment of the skull could be cut by the craniotome.
Furthermore, when negotiating a bony prominence of the skull, it was always difficult to strip the dura from the far or distant side of the bony prominence. Various forms of craniotomes have been developed including those with a rigid metal foot. One function of the metal foot is to strip the dura from the underside of the skull and even a rigid swiveling foot has been proposed. However, the rigid metal foot can not negotiate a bony prominence and thus present a significant risk to the patient.
The present invention marks a significant departure from the prior technique and provides an improved craniotome which permits continuous cutting of the skull between bur holes or from a single bur hole, and automatically strips the dura from the underside of the skull. Thus there is no need to remove the craniotome repeatedly and insert a separate instrument such as a spatula. Thus the surgical procedure for removing the skull portion is safer and may be performed more quickly. Also, the use of fewer, smaller bur holes is possible with the present invention thus reducing the amount of bone which is drilled away and hence non-replaceable, thus promoting more rapid healing and reducing disfigurement of the skull.